Nginx is a web server that can also be used as a reverse proxy, load balancer, mail proxy and HTTP cache.
Phusion Passenger is a free web server and application server with support for Ruby, Python and Node.js.
RackCache is a quick drop-in component to enable HTTP caching for Rack-based applications.
Ruby on Rails is a server-side web application framework written in Ruby under the MIT License.
Stripe offers online payment processing for internet businesses as well as fraud prevention, invoicing and subscription management.
Typekit is an online service which offers a subscription library of fonts.